磁流变阻尼器减振机理及旋转机械振动和稳定性主动控制

本项目研究磁流变阻尼器的减振机理及其在旋转机械振动及稳定性主动控制中的应用。分析磁流变流的力学特性，阻尼器非线性刚度和阴尼随外磁场的变化特性以及对旋转机械动态响应的影响。研究磁流变阻尼器用于转子振动控制的最佳闭环控制方案。磁流变阻尼器具有结构简单，反馈迅速及控制力大的优点，对旋转机械的减故延寿有较大的理论和实用价值。

Magnetorheological (MR) fluid is a kind of material that responds to an applied magnetic field with a dramatic change in rheological behaviour. With the characteristic of MR fluid, mechanical devices based on MR fluid have the ability to provide simple, quiet, rapid-response interfaces between electronic controls and mechanical systems. Hence, the research on MR fluid and applications has become an important branch in the field of intelligent materials. MR fluids will be extensively used in automobiles, machines, construction, medical treatment, etc., and are considered to be one of the most promising intelligent materials in the future. .MR fluid damper is one of the most important applications of MR fluid and is used to adjust the damping and stiffness of vibration systems, which is an ideal substitute to the passive control elements. In recent years, the studies on various MR fluids and MR dampers are increasing gradually, but literatures on vibration control of rotating machineries by MR fluid dampers are very less. .The study objective of this project is to explore the possibility of applying MR fluid in the vibration control of rotating machineries (especially rotors). So, theoretical analysis and experimental studies on MR fluid, MR fluid dampers and vibration control are the main topics of this project. Some new results are obtained in both theory and experiment, and the conclusions obtained can be used to guide the application of MR fluid damper in vibration and stability control of rotating machineries. .The main study contents and contributions are as follows:.(1) The research developments of MR fluids and their applications are comprehensively reviewed, including the general situation of the research on MR fluids as well as the compositions, properties, field-induced structures and applications of MR fluids. Especially, the classification for MR fluids by their compositions, the yield stress properties and the MR fluid dampers used in vibration control system are systematically summarized, and some existing problems in applications of MR fluid technology are pointed out. (2) Several types of homemade MR fluid are prepared, which are composed of carbonyl iron particles in micro size suspended in silicone oil. They have good magnetorheological properties and low viscosity, fulfill the demands of the experimental devices. In addition, an MR fluid brake is built, and its static braking torque is tested, which is used to analyze the static yield stress of the MR fluids. The testing shows that the static yield stress of the self-made MR fluid is over 41 kPa while the magnetic strength is 240 kA/m.(3) A linear MR damper with a moving piston is designed and manufactured, and is used to a motor-platform vibration-reducing experimental device. Four different nonlinear physic models of MR fluid damper are discussed and used to the theoretical analysis of the experimental system. It is found that the damping forces calculated by Bingham plastic model, bi-viscous model, hysteretic bi-viscous model and Bounc-Wen model can be well used to calculate the displacement and velocity responses of the vibration system, but the acceleration response calculated by the four models are different. It is found from the experiment that the response of the platform can reach a stable state very quickly when a control current is exerted, and the vibration amplitude is decreased with the increasing of the control current. This shows that the MR damper has a very high reaction speed, and the damping force is increased with the increasing of the magnetic strength. .(4) A shear mode MR fluid damper used for rotor vibration control is designed and manufactured, the calculating formula for the damping force is derived. The vibration characteristics and control method for a cantilever rotor system with single disk supported by the MR fluid damper are studied theoretically and experimentally. It is found that the Coulomb friction of the MR fluid damper increases with the increasing of the applied magnetic strength. As the Coulomb friction